1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor apparatus. More specifically the present invention relates to technique for adding conductive impurities to a semiconductor over a substrate.
2. Related Art
In case of forming an impurity region such as a source or a drain region that is a component of a thin film transistor (TFT), various methods for adding impurities are adopted.
As a method for adding impurities, for example, ion implantation, ion doping, or the like is utilized. The ion implantation is the technique, that is, elements such as boron (B), phosphorus (P), or the like is ionized and mass-separated, then, only necessary ions are accelerated by an electric field, and then, doped to a semiconductor such as silicon. The ion doping is the technique, that is, ions are accelerated by an electric field and doped without mass separation.
In case of utilizing such technique, only desired regions can be added with impurities by means of masking the region where doping is not wanted to be carried out.
However, there are problems that resist which is generally used as a mask is degassed by ion beam irradiation, due to this, pressure in a treatment chamber is increased, and so ion beam becomes impossible to be irradiated, an injection amount of impurities has a margin of error, or the like.
As technique for reducing degasification of resist, it is known that heating resist previously to remove degasification during doping (See Reference 1: Unexamined Patent Publication No. 5-55159).